linux-kernel - Re: [PATCH 04/16] x86: Replace cpu_2_logical

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Message-ID: <20110111141940.GB30607@htj.dyndns.org>
Date:	Tue, 11 Jan 2011 15:19:40 +0100
From:	Tejun Heo <tj@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	hpa@...or.com, x86@...nel.org, eric.dumazet@...il.com,
	yinghai@...nel.org, brgerst@...il.com, gorcunov@...il.com,
	penberg@...nel.org, shaohui.zheng@...el.com
Subject: Re: [PATCH 04/16] x86: Replace cpu_2_logical_apicid[] with early
 percpu variable

On Mon, Jan 10, 2011 at 07:48:41PM -0800, David Rientjes wrote:
> On Thu, 30 Dec 2010, Tejun Heo wrote:
> 
> > Unlike x86_64, on x86_32, the mapping from cpu to logical apicid may
> > vary depending on apic in use.  cpu_2_logical_apicid[] array is used
> > for this mapping.  Replace it with early percpu variable
> > x86_cpu_to_logical_apicid to make it better aligned with other
> > mappings.
> > 
> > Signed-off-by: Tejun Heo <tj@...nel.org>
> 
> The apicid's are now stored as int's as opposed to u8, even though the max 
> is 256.  Is that for extendability or for better alignment?  If not, I 
> think it would be better to keep the old type.

I don't know.  Yeah, it's x86_32 only so it can be u8 but other IDs
are shared with x86_64 and should be int.  I think it's less confusing
to simply use int.  It's not like the extra overhead is gonna be
noticeable or anything.

Thanks.

-- 
tejun
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